| AVS 65th International Symposium & Exhibition | |
| Actinides and Rare Earths Focus Topic | Wednesday Sessions |
| Session AC+MI+SA-WeM |
| Session: | Magnetism, Complexity, and Superconductivity in the Actinides and Rare Earths |
| Presenter: | Attila Bartha, Charles University, Prague, Czech Republic |
| Authors: | A. Bartha, Charles University, Prague, Czech Republic M. Klicpera, Charles University, Prague, Czech Republic P. Cermak, Forschungszentrum Juelich GmbH, Germany B. Ouladdiaf, Institute Laue-Langevin, France J. Custers, Charles University, Prague, Czech Republic |
| Correspondent: | Click to Email |
In the past decade, U-compounds crystallizing in the HoCoGa5-type structure (P4/mmm), frequently referred to as 115, have been in the focus of attention in experimental and theoretical research. Vigorous activities have been motivated by the high superconducting transition temperature of Tc = 8.7K in PuRhGa5 [1] and Tc = 18.5K in PuCoGa5 [2]. No further superconductivity has been reported in neither U-115 nor in the closely related U2TGa8 compounds (T = transition metal). However, interesting magnetic properties have been observed: neutron scattering experiments revealed that UNiGa5 exhibits the G-type antiferromagnetic (AFM) phase, while UPdGa5 and UPtGa5 exhibit the A-type AFM state. Note that G-type indicates a 3D Néel state, while A-type refers to a layered AF structure where spins align FM in the ab plane and AFM along the c axis [3]. The difference in the two magnetic structures is significant since it implies a sign change of the nearest-neighbor (NN) interaction.
Here we report on the magnetic structures of URhIn5 and U2RhIn8, two new members of the UnTmX3n+2m (X=In,Ga) family of compounds [4]. URhIn5 displays AFM order below TN = 98K. The observed increase of the resistivity for current parallel [100], [110] and [001] are reminiscent to a spin-density wave (SDW) type of transition with the gap opening first along the [001] direction [5]. U2RhIn8 enters the AFM state at TN = 117K. No increase in resistivity in the vicinity of TN is found which would hint to a SDW gap opening. Neutron diffraction experiments on URhIn5 were performed at the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching using the triple axis spectrometer PANDA. Single crystals with accumulated mass of 10mg where glued on an Al-plate. Our results confirmed the magnetic propagation vector k=(1/2,1/2,1/2) predicted by NMR experiments [6] and a magnetic moment of 1.65 µB/U3+. The neutron study on U2RhIn8 has been conducted at ILL, Grenoble using D10 on only one single crystal with m ≈ 1mg. Analysis revealed a propagation vector k=(1/2,1/2,0) and an ordered moment of 1.7 µB/U3+. UIn3, URhIn5 and U2RhIn8 all show G-type AFM phase. While the c-axis parameter differs significantly the a lattice parameter equals 4.601Å, 4.621Å and 4.6056Å respectively, being a change of less than 1% pointing to the fact that the NN coupling is important for the type of magnetic structure.
[1] F. Wastin et al., J.Phys.Condens.Matter 15, S2279 (2003)
[2] J.L. Sarrao et al., Nature (London) 420, 297 (2002)
[3] T. Hotta, Phys.Rev. B 70, 054405 (2004)
[4] A. Bartha et al., J.Magn.Magn.Mater. 381, 310 (2015)
[5] A. Bartha et al., Acta Phys.Pol. A 127, 339 (2015)
[6] H. Sakai et al. Phys.Rev. B 88, 045123 (2013)